Drip irrigation hose can be classified as having either discrete emitters or continuous integral emitters. An example of discrete emitters is shown in U.S. Pat. No. 4,850,531. An example of continuous integral emitters is shown in U.S. Pat. No. 4,247,051.
A design objective of drip irrigation hose is uniformity of the drip rate from each emitter. Since the water pressure in a drip irrigation system varies as a function of elevation of the field, it is customary to incorporate a pressure regulating mechanism into the emitters. Turbulent flow is less sensitive to pressure variation than laminar flow. Accordingly, it has become common practice for drip irrigation hose to employ a serpentine flow regulating passage as continuous integral emitters to promote turbulent flow. An example of such drip irrigation hose is disclosed in U.S. Pat. No. 4,984,739, where a series of staggered, upstream angled chevrons or weirs form the serpentine passage.
In a typical drip irrigation hose with continuous integral turbulent flow emitters, the emitters comprise a flow regulating passage formed by ribs that also seal the overlapping margins of an elongated bent sheet of plastic film. The passage is divided by cross ribs to form flow regulating segments. The bent film forms an elongated water supply passage having a large diameter. An inlet is formed from the water supply passage to one end of each segment of the flow regulating passage. An outlet is formed from the other end of each segment of the flow regulating passage to the exterior of the hose. Between the inlet and outlet, each segment has staggered, upstream angled chevrons.
Complications can occur when the dimensions of this type of drip irrigation hose are changed to increase the flow rate. Generally, the flow rate can be increased by decreasing the length of the segments, increasing the height of the ribs, or increasing the separation between the ribs of the flow regulating passage. However, these measures tend to decrease the reliability and uniformity of the product and to cause the water to squirt out of the outlets because the line pressure is not fully dissipated by the flow regulating passage.